As the conventionally known vacuum filling apparatuses of the above types, there has been formerly used one in which a container containing plural porous workpieces to be processes is put into an impregnating tank having a filling liquid therein, the impregnating tank is closely sealed by tightening its lid, the interior of the impregnating tank is deaerated under reduced pressure while the workpieces are kept immersed, the vacuum state is maintained for a prescribed time period, the workpiece container having the porous workpieces therein is taken out of the interior of the impregnating tank through opening its lid after the tank is returned to the atmospheric pressure. Moreover, a vacuum impregnating apparatus is known, which comprises an impregnating tank, a storage tank, an open air intake means, a vacuum pump, etc. and impregnates a liquid component or the like into a food dried under reduced pressure inside the impregnating tank. In addition, such a vacuum impregnating apparatus is known, in which a food is put in an impregnating tank, a lid of the impregnating tank is closed to hermetically seal the tank, the food is dried under reduced pressure, while a warming gas is introduced so that the food may not be frozen inside the impregnating tank, afterwards a liquid component or a gas component inside the storage tank is introduced into the impregnating tank, the interior of the impregnating tank is returned to the atmospheric pressure or pressurized after the pressure-reduced state is maintained for a prescribed time, the filling liquid is once extracted or lowered in level, the lid of the impregnating tank is opened, and the finished food is taken out of the tank. For instance, see JP2002-354988A, JP 2003-339328A, and JP2003-339328A.
However, the above conventional first vacuum filling apparatus has drawbacks that the filling rate is low and it takes a long time to perform the vacuum impregnation. Moreover, the above conventional second vacuum filling apparatus improves the filling rate, but the filler fluid component or the like needs to be put in and taken out of the impregnating tank. So, it takes an extra equipment and time. Though it is common to both the vacuum filling apparatuses, the lid fixed to the impregnating tank with a hinge or the like is opened and closed through loosing and tightening bolts or the like every one filling work, and the porous workpiece or food is moved into or out from the impregnating tank. Accordingly, it was difficult to shorten the working time.